1. Field of Invention
The invention relates to a light emitting device and process of making the same, and in particular to a light emitting diode package and process of making the same.
2. Related Art
A light emitting diode (LED) is a device that is composed of semiconductor material. It is also a solid source of light for transforming electricity into light. It is not only small in size but also has desirable properties such as long span life, low driving voltage, high response speed and shock resistance, which satisfy the applications requiring the properties of small, thin and light. Therefore, the LED has already become a common product in our daily lives and turned into a mature industry.
Generally, with an LED package such as the structure shown in FIGS. 1A and 1B, a LED chip is mounted on a substrate and surrounded by transparent epoxy for emitting light up or down. The light distribution curve of the structure is shown in FIG. 1C.
There are a few reasons for the growing demand for parallel sources of light. On the one hand, the vigorous growth of the LCD device increases the growing demand for parallel sources of light. On the other hand, parallel sources of light used in headlight or tail light industries can only be produced either from the light distribution curve, which is shown in FIG. 2 by using a light shield, or by using a light distribution curve produced by lamps, lanterns and LEDs, which are disclosed in PAL 2003 Symposium by Darmstadt University of Technology (please see the attachment). However, parallel sources of light produced by the structure described above require a large sized structure, which doesn't meet economic requirements. Therefore in order to satisfy the demand for parallel sources of light, there research is being done on LED devices to produce parallel light.
For example, please refer to FIGS. 3A and 3B, which show an LED package that emits light parallel to the substrate. The technique is disclosed in U.S. Pat. No. 6,627,922. The structure disclosed in FIG. 3A includes a light reflective element 10, an LED chip 14 and a substrate 16. The light reflective element 10 has an opening 12 at one side for emitting reflected light that is produced by the LED chip 14. The structure disclosed in FIG. 3B includes a rectangular insulation substrate 1, electrodes (2 and 3), an LED chip 4, a transparent element 6 and a light reflective element 7. The light reflective element 7 only covers part of the transparent element 6, and exposes the front and two sides of the transparent element 6. Therefore, light produced by the LED chip 4 can emit in parallel form from the front of the transparent element 6.
The prior art includes the following steps: mounting an LED chip 4 on a substrate; covering a transparent material on the LED chip 4 to form a transparent element 6; and then forming a light reflective element 7 above the transparent element 6. The process used to produce such an LED structure is complicated and costly. And because the light reflective element 7 is attached or mounted on the substrate 1, it may fall off and lose function. Further, the connection between the substrate 1, transparent element 6 and light reflective element 7 only depends on the strength of binding without any structural griping. Thus it is easily separated, which limits the application of the LED package. Due to its fragile structure, this kind of LED package is only suitable for low power applications, such as low power cell phones. And due to the limitation of the size of the structure, using several LED chips for mixing light may have several disadvantages, such as poor performance, poor optical properties and difficulty of designing the reflective surface.
Therefore, there is still a need for improving the LED package used to emit parallel light, which can simplify the process, reduce cost, increase the strength of the structure and improving the light mixing performance.